The radical Muslims who are making war on the world are confident they can win, destroy religious and ethical beliefs and cultures different from their own, and impose a worldwide caliphate.

Who can blame them? They believe in something — evil, ugly and malignant though it is. The West often acts like nobody believes anything. The jihadists cheerfully die in the name of their crusade to eradicate decency and democracy, taking as many innocents as they can with them. They're fighting a foe determined to protect ignorance of what moves those killers driven by their perverted "faith."

The very word "Islam" has become a word to frighten and intimidate, much like "Communist" was a fright word for an earlier generation. This is finally recognized by certain Muslims. Abdel-Fattah el-Sissi, the president of Egypt, thinks a religious revolution within Islam — perhaps like the Reformation of the Christianity blighted by the corruption of Rome — must purify and preserve his faith.

"It's inconceivable that the thinking that we hold most sacred should cause the entire [Muslim community] to be a source of anxiety, danger, killing and destruction for the rest of the world," he said in a courageous speech the other day at Cairo's thousand-year-old Al Azhar University. "The entire world, I say it again, is waiting for your next move."

This was courageous because the imams and leaders in the mosques have seen what the jihadis do even to members of their own kind who step out of line with a yearning to restore secular respectability for Islam. One of the police officers slain by the terrorists at the offices of Charlie Hebdo in Paris — the wounded officer shot execution-style while begging for life — was a devout Muslim.

But recognizing that many, indeed no doubt most, Muslims are peaceful and even respectful of other religions does not require giving Islam a pass for the transgressions by its followers against decency and order. George W. Bush, standing in the smoking ruins of Sept. 11, famously called Islam "a religion of peace" before all of the 2,996 bodies were recovered. Angela Merkel, the German chancellor, lectured her constituents against succumbing to "Islamophobia." But such exhortations by leaders in the West inevitably lapse into inane apologies for what makes Western civilization the fount of the freedoms of the modern world.

Barack Obama is a curious and special case. A fortnight after Ambassador Christopher Stephens and two other Americans were killed by Islamic terrorists at the U.S. embassy in Benghazi (when we were still trying to find out where Hillary was when the telephone rang a 3 o'clock in the morning), President Obama told the United Nations that "the future must not belong to those who slander the prophet of Islam." This week he could not bring himself to call the Muslim terrorists in Paris by their right name, and sent his press secretary out to offer a tepid wish and a flaccid wash to denounce an "act of violence," and use the occasion to offer another tribute to Islam as "a religion of peace."

Mr. Obama's curious timidity to stand up tall and straight to terrorism is catching. Howard Dean, once a Democratic candidate for president of the United States (best remembered for his valedictory of crying out a roll call of the states), scolded those who decry the culpability of Islam in the terror that intimidates its own believers. "I stopped calling these people Muslim terrorists," he said. "They're about as Muslim as I am. I mean I think ISIS is a cult. Not an Islamic cult." He had better be careful. The men with the beheading knives don't agree with him.

The Islamic radicals have neither respect nor fear for the decent and democratic strengths and traditions of the West, but they know how to exploit them for their own uses. They can rail as loud as any small-d democrat, libertarian or ACLU liberal about Western governments granting broad authority to watch and interrogate those who set out to destroy America, counting on the convictions of free men to protect them in their evil.

The proper message to the Islamic world from American presidents, whether Democratic or Republican, is that "your religion may be a religion of peace, but we trust and verify." If high-church Episcopalians are caught blowing up hospitals and blue-haired Lutheran ladies from Minnesota, Baptists from Alabama, and Methodists from Ohio are caught burning schools in the name of their faith, they'll have to prove theirs is a religion of peace, too. Civilization is based on faith, but faith without works is dead. Presidents should say that, too.